Mixed extractant and process for separating copper from cobalt and nickel in acid medium



3,455,680 MIXED EXTRACTANT AND PROCESS FOR SEPARATING COPPER FROM COBALTAND NICKEL IN ACID MEDIUM Allan W. Ashbroolr, Ottawa, Ontario, Gordon M.Ritcey, Bells Corners, Ontario, and Edwin G. Joe. Ottawa, Ontario,Canada, assignors to Canadian Patents and Development Limited NoDrawing. Filed Mar. 3, 1966, Ser. No. 531,377 Int. Cl. C22b 15/08, 23/04U.S. Cl. 75-117 8 Claims ABSTRACT OF THE DISCLOSURE A process forseparating copper from nickel and cobalt in an aqueous acid leach mediumin which the medium is contacted with a mixed extraction reagent at a pHof 0.5 to 3. The reagent consists of an inert organic solvent havingdissolved therein 30% by volume of di-(2-ethylhexyl)phosphoric acid and5-30% by volume of an a-hydroxy oxime (LIX 63).

This invention relates to the separation of copper from cobalt andnickel in an acid solution in which the three metals are dissolved and,more particularly, to a process in which a mixed extraction reagentcomprising an organo phosphoric acid compound and an a-hydroxy oxime isused in the liquid-liquid separation of copper from cobalt and nickel inan acid solution or acid leach slurry.

Processes are known for extracting copper from solutions usingorganophosphoric acid compounds, e.g. Olson et al., United States PatentNo. 3,104,971, issued Sept. 24, 1963. It is also known to use a-hydroxyoxime for this purpose, e.g. Swanson, United States Patent No. 3,224,-873, issued Dec. 21, 1965. However, the mixed extraction reagent of thisinvention has been found to provide much more efficient extractions atlower pH levels than could be obtained with either the organo phosphoricacid compound or the a-hydroxy oxime used separately. Thus, it appearsthat synergism exists between the two components, which providessuperior results when the two components are used mixed together.According to the process of the invention, an acid solution or acidleach slurry containing copper, cobalt and nickel is subjected toliquidliquid solvent extraction with a mixed solvent extraction reagentcomprising an organophosphoric acid and an a-hydroxy oxime dissolved inan inert organic solvent. During the extraction the organic phasebecomes loaded with copper while the nickel and cobalt remain in theraffinate.

The two phases are then separated and the organic phase, containing thecopper, is treated with dilute mineral acid to strip the copper. Thenickel and cobalt can be selectively extracted from the aqueous phase byfurther contacting with the mixed extraction reagent or by other knownmethods.

The organo phosphoric acid component of the mixed solvent extractionreagent which can be used according to this invention is advantageouslyan organo phosphoric acid compound of the following formula where R isselected from the group consisting of alkyl, aryl, and aralkyl radicals.Since the compound must be substantially Water-immiscible, the totalnumber of carbon atoms in the molecule should be sufficient to rendernitecl States Patent 0 3,455,68d Patented July 15, 1969 "ice thecompound substantially insoluble. Generally at least 8 carbon atomsshould be present. The R group can, of course, be substituted with avariety of groups such as alkoxy, halogens, etc., and R can be saturatedor unsaturated or interrupted by hetero atoms so long as there is nointerference in the performance of the compound in extracting copperions from the aqueous phase to the organic phase.

Particular organophosphoric acid compounds which can can beadvantageously used according to this invention include di(Z-ethylhexyl)phosphoric acid, heptadecylphosphoric acid, dodecylphosphoric acid,di(l-methylheptyl) phosphoric acid, diisooctylphosphoric acid, di(2-ethyl-4-methylpentyl) phosphoric acid, di(2-propyl-4- methyl-pentyl)phosphoric acid, octylphenyl phosphoric acid, the isooctyl or stearylderivatives of alkyl acid phosphates, and the like.

The a-hydroxy oxime component has the general formula OH NOH where R, Rand R" may be any of a variety of organic hydrocarbon radicals such asaliphatic and alkylaryl radicals. R" may also be hydrogen. Preferably, Rand R are unsaturated hydrocarbon or branched chain alkyl groupscontaining from about 6 to 20 carbon atoms. R and R are also preferablythe same and, when alkyl, are preferably attached to the carbonssubstituted with the OH and =NOH groups through a secondary carbon atom.It is also preferred that R" is hydrogen or unsaturated hydrocarbon orbranched chain alkyl groups containing from about 6 to 20 carbon atoms.The u-hydroxy oximes also preferably contain a total of about 14 to 40carbon atoms. Representative compounds are19-hydroxyhexatriaconta-9,27-dien-l8-oxime, S-IO-diethyl 8hydroxytetradecan-7-oxime, and 5,8-diethyl-7-hydroxy-dodecane- 6-oxime.The latter compound has the following structural formula:

Representative of other monoand polyunsaturated radicals are heptenyl,octenyl, decenyl, octadecenyl, octadecynyl and alkyl substitutedradicals such as ethyloctadecenyl. Representative of other monoandpolyalkyl substituted saturated radicals are ethylhexyl, diethylheptyl,butyldecyl, butylhexadecyl, ethylbutyldodecyl, butylcyclohexyl and thelike.

The a-hydroxy oxime component is also characterized as having asolubility of at least 2% by weight in the hydrocarbon solvent used tomake up the organic phase and substantially complete insolubility inwater.

The a-hydroxy oximes are prepared by reacting an acyloin with ahydroxylamine salt under reflux conditions. Such reaction can be carriedout by refluxing the reactants in an alcohol such as ethanol and addingpyridine to combine with the acid associated with the hydroxylamine.

A wide variety or organic diluents, in which the extraction reagent isdissolved, can be employed according to this invention. The minimumrequirements for the diluent, however, are that the diluent besubstantially water-immiscible, that it will dissolve the extractionreagent, and that it will not interfere with the fitnction of thereagent in extracting the copper values from acid solutions. Thesediluents can be aliphatic or aromatic hydrocarbons, halogenatedhydrocarbons, petroleum derivatives, ethers, etc. Examples of thesevarious diluents include toluene, carbon tetra-chloride, benzene,chloroform, Z-ethyl-hexanol,

rated, the copper containing organic phase is transferred to a strippingcircuit which can be any suitable liquidliquid contactor. In thestripping circuit the copper-containing organic phase is advantageouslycontacted with 2-20% by volume of a mineral acid, e.g. sulphuric, nitricand particularly kerosene. 6 or hydrochloric, the choice of aciddepending on the cop- The ratio of the components in the mixed solventexper salt required. traction reagent can be varied over a wide range.How- The cobalt and nickel remaining in the aqueous phase ever, forpractical purposes, the volume percent of each can be separated by anysuitable method, such as those constituent in the mixture can vary fromabout to 10 described in co-pending Ashbrook et al. application about30%. Ser. No. 465,750 filed June 21, 1965 and Ritcey et al.

It has also been found to be desirable to incorporate an applicationSer. No. 465,789 filed June 21, 1965. It is additive in the solventmixture to inhibit emulsions and also possible to separate the cobaltand nickel remaining assist in phase separation. Long chain aliphaticalcohols in the aqueous phase by again contacting this phase with arewell suited for this purpose and isodecanol has been the mixedextraction reagent of the invention. In this found to be particularlysuitable. extraction the cobalt values are transferred to the or-Contacting of the acid solution containing the copper, ganic phase whilethe nickel values remain in the aquenickel and cobalt values with thesolvent extraction ous phase. The cobalt can then be stripped from thereagent may be carried out by any of the well-known organic phase.procedures employed in solvent-solvent extractions. Al- The acidsolution is prepared by first leaching an ore though continuouscountercurrent methods are preferred, containing copper, nickel andcobalt with an acid. Nitric batch, continuous batch, and batchcountercurrent methor sulphuric acid has been found to be the mostsuitable ods are also useful. Any suitable liquid-liquid contacting forthe leaching step. After leaching, the leach slurry may means may beemployed. such as a pulse column, a be filtered to obtain a solutioncontaining copper, nickel countercurrent rotating disc column, and thelike. The and cobalt, or the leach slurry may be contacted directlytemperature at which the mixing is carried out is not with the mixedextraction reagent according to the incritical, but advantageously thetemperature is maintained vention. From an economic standpoint there isconsiderat about 20 C. to 40 C. able advantage in conducting theextraction directly on the The extraction preferably takes place at a pHin the leach slurry. range of about 0.5 to about 3.0. A low pH has beenThe invention will now be illustrated by reference to the found to beparticularly desirable since the selectivity of following non-limitativeexamples: metal separation is better with the low pH. An importantconsideration in determining the pH level of the extrac- EXAMPLE 1 tionis the amount of iron and aluminium to be found in A series of liquidextractions were conducted o a the acid solution. Thus, in order toassure high loading Solution wnifliniflg g- Ni and g-/lin the organicphases, the pH must be adjusted bov Co, using as extraction solventShell 140 Flash Naphtha that level where iron will precipitate and belowthe precont ining varying amounts of a mixture of di(2-ethyleipitationpH (approximately 3.8 to 4) of aluminium. 1f 3 PhOSPhOFiC acid and Y YOXimB available appreciable iron is in solution, this will precipitateand m General M 1116- d r th t d ark LIX-63. cause emulsions in theorganic-aqueous contact. If alumin- The extraction was carried out at anequ P 0f ium is allowed to precipitate, emulsions are also formed. 11-5-The ratio of the volume of the organic phase to the The feed pH was1.85, the aqueous to organic ratio aqueous phase can be variedconsiderably and the most a 111 an t HtaC t m W s 5 minut sefiicientratio in each case can be readily determined by The results of theseextractions are tabulated in Table one skilled in the art. Theparticular ratio selected for A below:

TABLE 11 l i e xi ls y Extraet,g./l. Raffinate, .,/1. E 1 e iiii i i LIXCu Ni 00 Cu Ni Co iiii 1 0.0 0.1 0.1 4.7 5.0 5.0 1.5 3 1.7 0.1 0.1 4.05.1 5.3 1.5 5 2.5 0.1 0.1 3.4 4.0 4.8 1.2 7 3.2 0.1 0.1 2.7 4.8 4.5 1.110 3.5 0.1 0.2 1.0 4.8 5.1 1.1 15 4.0 0.1 0.3 1 5 5.2 5.1 1.1 20 4. 30.1 0. 3 1. 5 5.1 4. s 1.1 5 1.2 0.1 0.1 4.5 5.3 5.7 1.5 5 2. 0 0. 1 0.13.5 5. 4 5. 0 1. 4 5 2. 0 0. 1 0. 1 3. 0 5. 4 5. 0 1. a 5 3.2 0.1 0.12.7 5.5 5.7 1.3 5 3. 2 0.1 0. 1 2. 5 5.2 5. 7 1. a 5 3. 2 0.1 0.1 2. 25. 2 s. 0 1. 3

any given extraction may depend upon the extraction EXAMPLE 2 reagent,diluent, and type of copper bearing solution employed as well as theirconcentration and the method of mixing them, etc. Countercurrent methodsare usually desirable when the ratio of the organic phase to the aqueousphase is relatively low. It has been found that for extraction in apulse column, an organic to aqueous ratio of about 1:1 is verysatisfactory.

After the copper values have been transferred to the organic phase andthe aqueous and organic phases sepa- Tests were also conducted on leachslurry obtained by acid leaching of a uranium refinery residue of thegeneral type having the following analysis:

TABLE B Element Percent (wt. dry basis) Ag 0.006 As -2 2.2

Element Percent (wt. dry basis) Co 1.76 CO 10.1 Cu 2.20

Ni 0.90 U 0.25

(a) Leaching A refinery residue of the above type was leached withsulphuric acid for 2 hours at a temperature of 60 C. A 90% dissolutionor over of copper, cobalt and nickel Was achieved with the addition of1000 pounds of sulphuric acid per ton of residue. The leach slurrycontained about 20% solids.

(b) Extraction equipment The equipment used to extract the nickel,copper and cobalt from the leach slurry is a pulse column consisting ofa 6 inch diameter by 2 foot long Pyrex feed chamber and organicoverflow, a 30 foot long 2 inch diameter Pyrex pipe section with 180stainless steel dispersion plates at 2 inch intervals and an expandeddischarge section for emulsion disengagement. The dispersion plates haveinch diameter holes sufiicient to yield a 34% open area. The pulse issupplied by a single stroke diaphragm pump with variable amplitude andfrequency adjustment. Organic flow is metered through a flow rotor. Pulpfeed and discharge rates are controlled by variable speed finger pumps.

(c) Extraction of copper A copper extraction was conducted with theabove equipment on a leach slurry feed containing 0.05 g./l. uranium,6.4 g./l. copper, 2.8 g./l. nickel and 5.1 g./l. cobalt.

The organic employed in this circuit was a di- (2-ethylhexyl)phosphoricacid plus 10% LIX-63 in 140 Flash Naphtha with 3%. isodecanol added asan emulsion suppressant.

The operating conditions were as follows:

Total flow 8 gals/hr.

Aqueous/organic ratio 1:1.

Pulse amplitude inch.

Pulse frequency 52.

Start pH 2.5.

Terminal pH 2.2.

NH OH added 1 1% of aqueous flow as 1.2 M

NH OH.

lhe NH-iOH was added to the aqueous flow to maintain the pH above 2.0.

An analysis of the organic phase showed .001 g./l. uranium, 6.5 g./l.copper, 0.014 g./l. nickel and 0.017 g./l. cobalt while the raffinatecontained 0.05 g./l. uranium and 0.04 g./l. copper.

(d) Stripping of copper The copper was stripped from the organic phaseby an 80 g./l. H 50 solution at 50 C. in a pulper-decanter circuit. Thestripping efiiciency obtained was 86% leaving a copper residual of lessthan 1 g./l. in the stripped organic.

The stripped liquor can be recirculated to crystallization orelectrolysis.

(e) Extraction of cobalt The ratfinate from the copper extraction wasneutralized to pH 4 and extracted in a pulse column with an organic feedconsisting of a 10% di(2-ethylhexyl)phosphoric acid plus 10% LIX-63 in140 Flash Naphtha. Ammonium hydroxide was added along the column tomaintain the pH above 3. At a total flow rate of 8 gallons per hour withan organic to aqueous ratio of 1:1, over 90% of the cobalt was extractedin the organic. However, the organic contained 0.16 g./l. Ni and only3.58 g./l. Co yielding a nickel impurity in the cobalt of about 5%.

This nickel level can be reduced to less than 1% but recovery of cobaltwould be lessened to 50%. The cobalt was readily stripped with 10% HNOThe strip solution after several recycles can be boiled down to thenitrate form or calcined to produce cobalt oxide powder.

(f) Recovery of nickel The cobalt circuit rafiinate was neutralized topH 6 with lime and filtered. The nickel was then precipitated withsodium carbonate.

We claim:

1. A process for separating copper from nickel and c0- balt in anaqueous acid leach medium containing the above metals, which comprisescontacting said medium with a mixed extraction reagent at a pH in therange of 0.5;to 3, the mixed extraction reagent comprising an inertorganic solvent having dissolved therein (a) 5-30% by volume of anoragno phosphoric acid compound having the formula wherein each R is analkyl radical and the R groups together contain at least 8 carbon atomsand (b) 5-30% by volume of an a-hydroxy oxime having a solubility of atleast 2% by weight in the organic solvent and having the formula 0HlfiIOH |o-P.' RI

where R and R are selected from the group consisting of unsaturatedhydrocarbon radicals and branched chain alkyl groups containing 6 to 20carbon atoms and R" is selected from the group consisting of hydrogenand unsaturated hydrocarbon radicals and branched chain alkyl groupscontaining 6 tto 20 carbon atoms, whereby the copper values areextracted from the aqueous phase to the organic phase and separating theresultant copper loaded organic phase from the aqueous phase.

2. A process according to claim 1 wherein the medium is an acid leachsolution.

3. A process according to claim 1 wherein the medium is an acid leachslurry.

4. A process according to claim 1 wherein the ahydroxy oxime contains atotal of from about 14 to 16 carbon atoms.

5. A process according to claim 1 wherein the copper is stripped fromthe organic phase by treatment with a dilute mineral acid.

6. A process according to claim 1 wherein the organo phosphoric acidcompound is di(2-ethylhexyl)phosphoric acid.

7. A process according to claim 1 wherein the inert organic solvent iskerosene.

8. A process according to claim 1 wherein the mixed extraction reagentcontains about 3-5% of a long chain aliphatic alcohol as emulsioninhibitor.

References Cited UNITED STATES PATENTS 3,104,971 9/1963 Olson et a175-1l7 3,224,873 12/1965 Swanson 75---101 2,992,894 7/ 1961 Hazen et al.75-117 3,276,863 10/ 1966 Drobnick et al 75-117 L DEWAYNE RUTLEDGE,Primary Examiner T. R. FRYE, Assistant Examiner US. Cl. X.R.

